Project Summary/Abstract The broad, long term goal of the proposed study is to determine, at the molecular level, mechanisms by which chromatin structure is regulated for proper cell cycle control. Chromatin regulation plays integral roles in a wide variety of DNA-dependent processes, including transcription, DNA replication, DNA repair, recombination, kinetochore formation, and DNA damage checkpoint response. Therefore, elucidating the mechanisms of chromatin regulation is a necessary prerequisite for understanding how these essential processes are controlled. One of the major challenges in studying chromatin regulation is to elucidate how chromatin regulation affects such a wide variety of processes in the contexts of important biological processes, such as cell cycle control and cell division. This is a particularly important challenge, because it was recently determined that mutations in chromatin regulators represent one major class of so called cancer driver mutations, and how these mutations accerelate cancer development remains unknown. Therefore, elucidating the mechanisms of chromatin regulation impacts not only the researchers who study fundamental principle of DNA-dependent processes, but also those who investigate cancer biology and mechanisms of genome stability maintenance. Our lab is interested in understanding how chromatin regulation contributes to proper cell division and cell cycle progression. We have recently started investigating molecular mechanisms underlying cell quiescence. Proper control of quiescence is essential for the maintenance of stem cell population and prevention of cancer. However, molecular mechanisms that control the entry and maintenance of quiescent cell state have been largely unknown. It was recently found that the budding yeast S. cerevisiae can enter quiescent state that share many properties with mammalian quiescence, and a method to purify the quiescent cell was developed. Taking advantage of this system, we have found a highly conserved chromatin regulator plays central roles in the entry into quiescence. We have also found that two highly conserved chromatin regulators are targeted to ribosomal RNA genes and control their transcription in a manner highly regulated by growth cues. We will take advantage of these recent findings and determine how chromatin regulation contributes to proper quiescence entry and cell division control. In addition, we are in a highly unique position to address a long-standing question of how local chromatin structure affects global chromatin architecture using a breakthrough new method that was very recently developed. Taking advantage of this novel technique, we will address this important, previously unapproachable issue.